The present invention relates to an airfoil for a nozzle stage of a gas turbine and particularly relates to a novel and improved airfoil and annulus profile for the first-stage nozzle of a combined air and steam-cooled gas turbine.
In the development of an advanced combined air and steam-cooled gas turbine, many specific requirements must be met for each stage of the hot gas path section of the turbine in order to meet the design goal, in this instance, a 60% combined-cycle efficiency goal. Particularly, the first stage of the turbine section must meet efficiency, heat load, life, throat area and vectoring requirements to meet that goal. Conventional nozzle designs do not allow for the added benefit of advanced three-dimensional aerodynamics that improve the use of the combustion gases to improve blade loading sufficiently to meet that goal.
In accordance with a preferred embodiment of the present invention, there has been developed an airfoil shape, as well as a configuration of the inner and outer bands for a nozzle stage of a gas turbine, preferably the first stage nozzle, that enhance the performance of the gas turbine. The nozzle airfoil hereof is characterized by a high degree of bow in the trailing edge, as well as in the body of the airfoil. It is this bow that causes improved total pressure and momentum in the stage 1 bucket which increases the efficiency of the turbine section of the engine. The nozzle stage hereof improves the interaction between various stages in the turbine, affords improved aerodynamic efficiency through the first stage and improves the first stage blade loading. Thus, it is the profile of the airfoil and the surface configuration of the inner and outer bands which define the hot gas path annulus about the nozzle stage which meet the requirements for stage efficiency as well as parts life and manufacturing.
In a preferred embodiment according to the present invention, there is provided an airfoil for a gas turbine nozzle stage having a profile at ambient temperature substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table I wherein Z is a height from a plane through a horizontal centerline of the turbine and X and Y are coordinate values defining the profile at each distance Z from the plane through the horizontal centerline of the turbine, the values being in inches and having a tolerance of +0.165 to xe2x88x920.135.
In a further preferred embodiment according to the present invention, there is provided a nozzle stage for a gas turbine comprising forty-two airfoils spaced equally one from the other about a horizontal centerline of the gas turbine, each airfoil having a profile at ambient temperature substantially in accordance with Cartesian coordinate values of X, Y and Z set forth in Table I wherein Z is a height from a plane through a horizontal centerline of the turbine and X and Y are coordinate values defining the profile at each distance Z from the plane through the horizontal centerline of the turbine, the values being in inches and having a tolerance of +0.165 to xe2x88x920.135.